Electrode structure of a carrier substrate of a semiconductor device

ABSTRACT

It is an object to provide an electrode structure of a carrier substrate of a semiconductor device in which the strength and the reliability of the joint portion between an electrode of a semiconductor package and an electrode of a main substrate are improved. A soldering land ( 103 ) that is an electrode of a carrier substrate ( 102 ) is hemispheric having a concentric hemispheric face hollow portion thereinside, a flange portion is provided in the circumferential portion thereof, and the outer diameter of the flange portion corresponds to the outer diameter of the conventional cylinder. Two slits ( 104 ) are provided in the flange portion and parts of a wall surface adjacent to the flange portion for venting air. A hemispheric face recess is provided in the carrier substrate ( 102 ) toward an outer surface, and the soldering land ( 103 ) is fixedly attached to the carrier substrate ( 102 ) so that the soldering land ( 103 ) is fitted into the recess and the flange portion abuts the outer surface of the carrier substrate.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to an electrode structure of asemiconductor device for solder-bonding to a main substrate.

[0003] 2. Description of the Related Arts

[0004] In order to make personal home electric appliances such as aportable telephone, a video camera, and a personal computer small,compact, lightweight, the package of a semiconductor device has beenchanged from an LSI package having a gull-wing type lead electrode to aBGA (ball grid array) type or a CSP (chip scale package) type which arecompact, lightweight packages. FIG. 5 is an outward view of a BGA typepackage semiconductor device, and (a) is a side view and (b) is a bottomview. FIG. 6 is a partial side view of a state where the BGA typepackage semiconductor device of FIG. 5 is bonded to a main substrate.The semiconductor element which is mounted to a carrier substrate 502and is not shown in the drawing is sealed in a package composed of aresin part 501 and the carrier substrate 502, and an external terminalof the semiconductor element is connected to an external part via asoldering land 503 that is an electrode grid-like arranged on thecarrier substrate 502. A soldering land 602 is provided at a positioncorresponding to the soldering land 503 of the carrier substrate 502 ofthe semiconductor device in the main substrate 601 in which thesemiconductor device is mounted and is bonded to the soldering land 503of the semiconductor substrate via solder 603. Both soldering land 503and soldering land 602 have cylindrical shapes with low heights, theirupper faces are generally smooth flat faces, and the smooth upper facesof both lands are bonded across the solder 603.

[0005] The interval of the lands becomes narrow and the areas of landsbecome small with miniaturization of a package, and thus a problem thatthe joint strength and the reliability of the lands by means of thesolder become low has occurred.

[0006] It is an object of the present invention to provide an electrodestructure of a carrier substrate of a semiconductor device in which thestrength and the reliability of the joint portion between an electrodeof a semiconductor package and an electrode of a main substrate areimproved.

SUMMARY OF THE INVENTION

[0007] An electrode structure of a carrier substrate of a semiconductordevice of the present invention is an electrode structure of a carriersubstrate of a semiconductor device for solder-bonding the semiconductordevice to a main substrate, wherein a recess is formed in a central areaof the electrode, and the electrode has a through portion passingthrough between the recess and an outer portion of a circumferentialwall surface surrounding the recess of the central area, on thecircumferential wall surface.

[0008] The electrode may be hemispheric having a flange portion and hasa concentric hemispheric face hollow portion thereinside, thehemispheric portion of the electrode may be fitted into a hemisphericrecess provided on an outer surface in the carrier substrate of thesemiconductor device, and the electrode may be fixedly attached to thecarrier substrate so that the flange portion abuts the outer surface ofthe carrier substrate. The through portion passing through between therecess and the outer portion of the wall surface may be at least oneslit provided in the flange portion and the wall surface of theelectrode adjacent to the flange portion.

[0009] The electrode may be cylindrical having a flange portion and hasa concentric cylindrical hollow portion thereinside, the cylindricalportion of the electrode may be fitted into a cylindrical recessprovided on an outer surface in the carrier substrate of thesemiconductor device, and the electrode may be fixedly attached to thecarrier substrate so that the flange portion abuts the outer surface ofthe carrier substrate. The through portion passing through between therecess and the outer portion of the wall surface may be at least oneslit provided in the flange portion and the cylindrical wall surface ofthe electrode adjacent to the flange portion to a position close to abottom.

[0010] The package of the semiconductor device may be of a BGA type or aCSP type.

[0011] By forming a recess in a central area of the electrode, a jointarea between a soldering land and solder increases, and the joint isthree-dimensional. Further, since a through portion connecting therecess and the outer portion of the wall surface is provided, the airthereinside escapes, and solder becomes wet and spreads in the recessfully, whereby the same strength joint can be achieved by a small amountof solder and the interval between the carrier substrate and the mainsubstrate can be narrowed

BRIEF DESCRIPTION OF THE DRAWINGS

[0012]FIG. 1 is a schematic view showing an electrode structure of acarrier substrate of a semiconductor device of a first embodiment of thepresent invention, and (a) is a plan view, (b) is a side sectional viewtaken on the line A-A of (a), and (c) is a side sectional view taken onthe line B-B of (a);

[0013]FIG. 2 is a partial side view of a state where the carriersubstrate of the semiconductor device of FIG. 1 is bonded to a mainsubstrate;

[0014]FIG. 3 is a schematic view showing an electrode structure of acarrier substrate of a semiconductor device of a second embodiment ofthe present invention, and (a) is a plan view and (b) is a sidesectional view taken on the line C-C of (a);

[0015]FIG. 4 is a partial side view of a state where the carriersubstrate of the semiconductor device of FIG. 3 is bonded to a mainsubstrate;

[0016]FIG. 5 is an outward view of a BGA type package semiconductordevice, and (a) is a side view wand (b) is a bottom view; and

[0017]FIG. 6 is a partial side view of a state where the BGA typepackage semiconductor device of FIG. 5 is bonded to a main substrate.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0018] It is an object of the present invention to improve the structureof a soldering land that is an electrode for improving the reliabilityof a solder joint portion of a semiconductor device and particularly toimprove the structure of a soldering land in a ball grid array package(hereafter, BGA) and a chip size package (hereafter, CSP) of an LSI.

[0019] Next, embodiments of the present invention are explainedreferring to drawings. FIG. 1 is a schematic view showing an electrodestructure of a carrier substrate of a semiconductor device of a firstembodiment of the present invention, and (a) is a plan view, (b) is aside sectional view taken on the line A-A of (a), and (c) is a sidesectional view taken on the line B-B of (a). FIG. 2 is a partial sideview of a state where the carrier substrate of the semiconductor deviceof FIG. 1 is bonded to a main substrate.

[0020] Referring to FIG. 1, a soldering land 103 that is an electrode ofa carrier substrate 102 which was conventionally cylindrical ishemispheric having a hollow portion of a concentric hemispheric facethereinside and is provided with a flange portion in the circumferentialportion thereof in the first embodiment, and the outer diameter of theflange portion corresponds to the outer diameter of the conventionalcylinder. Two slits 104 are provided in the flange portion and parts ofa wall surface of the soldering land 103 adjacent to the flange portionfor venting air. A hemispheric face recess is provided in the carriersubstrate 102 toward an outer surface, and the soldering land 103 isfixedly attached to the carrier substrate 102 so that the soldering land103 is fitted into the recess and the flange portion abuts the outersurface of the carrier substrate.

[0021] A semiconductor element which is mounted to the carrier substrate102 and is not shown is sealed in a package composed of a resin part 101and the carrier substrate 102, and an external terminal of thesemiconductor element is connected to an external part via the solderingland 103 that is an electrode grid-like arranged on the carriersubstrate 102.

[0022] As shown in FIG. 2, a soldering land 202 is provided at aposition corresponding to the soldering land 103 of the carriersubstrate 102 of the semiconductor device in the main substrate 201 inwhich the semiconductor device is mounted, and solder printing isimplemented on the main substrate 201. Then, BGA and CSP having thehemispheric soldering land 103 having the recess are mounted to the mainsubstrate 201 so that the soldering land 202 of the main substrate 201and the soldering land 103 of the BGA and the CSP corresponding theretoare matched.

[0023] Then, these are thrown into a reflow furnace for soldering,printed solder 203 is melted, and the solder 203 becomes wet and startsspreading over the soldering land 202 of the main substrate 201 and thesoldering land 103 of the BGA and the CSP. Air stagnates in the recessof the soldering land 103 of the BGA and the CSP, and usually the airprevents the solder 203 from invading into the recess. However, in thefirst embodiment of the present invention, since the air inside therecess escapes via the slits 104 shown in FIG. 1, it becomes possiblefor the solder 203 to become wet and spread in the recess fully. Whenthey are taken out from the reflow furnace, the solder hardens, and thesoldering land 202 of the carrier substrate 102 is bonded to thesoldering land 202 of the main substrate 201.

[0024] By changing the structure of the soldering land 103 from aconventional flat face to a recess, the solder joint area can beincreased, and the reliability of the joint portion can be improved.

[0025] In the explanation above, although the shape of the solderingland 103 is hemispheric having a hollow portion of a concentrichemispheric face thereinside and is provided with a flange portion inthe circumferential portion thereof, the shape may be cylindrical havinga hollow portion of hemispheric face thereinside, and a slit for ventingair may be provided.

[0026] Next, a second embodiment of the present invention is explainedreferring to drawings. FIG. 3 is a schematic view showing an electrodestructure of a carrier substrate of a semiconductor device of the secondembodiment of the present invention, and (a) is a plan view and (b) is aside sectional view taken on the line C-C of (a). FIG. 4 is a partialside view of a state where the carrier substrate of the semiconductordevice of FIG. 3 is bonded to a main substrate.

[0027] Referring to FIG. 3, a soldering land 303 that is an electrode ofa carrier substrate 302 which was conventionally cylindrical iscylindrical having a concentric cylindrical hollow portion thereinsideand is provided with a flange portion in the circumferential portion ofthe upper portion thereof in the second embodiment, and the outerdiameter of the flange portion corresponds to the outer diameter of theconventional cylinder. This is a similar structure to a through-hole andcan be formed by a similar manufacturing method. Two slits 304 areprovided in the flange portion and in a wall surface adjacent to theflange portion to positions close to the bottom face for venting air. Acylindrical recess is provided in the carrier substrate 302 toward anouter surface, and the soldering land 303 is fixedly attached to thecarrier substrate 302 so that the soldering land 303 is fitted into therecess and the flange portion abuts the outer surface of the carriersubstrate.

[0028] A semiconductor element which is mounted to the carrier substrate302 and is not shown is sealed in a package composed of a resin part 301and the carrier substrate 302, and an external terminal of thesemiconductor element is connected to an external part via a solderingland 303 that is an electrode grid-like arranged on the carriersubstrate 302.

[0029] As shown in FIG. 4, a soldering land 402 is provided at aposition corresponding to the soldering land 303 of the carriersubstrate 302 of the semiconductor device in the main substrate 401 inwhich the semiconductor device is mounted, and solder printing isimplemented on the main substrate 401. Then, the BGA and the CSP havingthe cylindrical soldering land 303 having the hollow portion are mountedto the main substrate 401 so that the soldering land 402 of the mainsubstrate 401 and the soldering land 303 of the BGA and the CSPcorresponding thereto are matched.

[0030] Then, these are thrown into a reflow furnace for soldering,printed solder 403 is melted, and the solder 403 becomes wet and startsspreading over the soldering land 402 of the main substrate 401 and thesoldering land 303 of the BGA and the CSP. Air stagnates in the hollowportion of the soldering land 303 of the BGA and the CSP, and usuallythe air prevents the solder 403 from invading into the hollow portion.However, in the second embodiment of the present invention, since theair inside the hollow portion escapes via the slits 304 shown in FIG. 3,it becomes possible for the solder 403 to become wet and spread fully.When they are taken out from the reflow furnace, the solder hardens, andthe soldering land 303 of the carrier substrate 302 is bonded to thesoldering land 402 of the main substrate 401.

[0031] By changing the structure of the soldering land 303 from aconventional flat face to a cylinder having a hollow portion, the solderjoint area can be increased, and the reliability of the joint portioncan be improved.

[0032] As described above, the present invention produces the followingadvantageous effects.

[0033] A first advantageous effect is that the strength and thereliability of a solder joint portion can be improved. This is becausethe joint area between a soldering land and solder is increased and thejoint is three-dimensional.

[0034] A second advantageous effect is that the height of mounting canbe restrained since the amount of solder of the solder joint portion canbe reduced. This is because the same strength joint can be achieved by asmall amount of solder and the interval between the carrier substrateand the main substrate can be narrowed since the joint between thesoldering land and solder becomes three-dimensional, and thus the solderinvades the inside of the soldering land.

What is claimed is:
 1. An electrode structure of a carrier substrate ofa semiconductor device for solder-bonding the semiconductor device to amain substrate, wherein a recess is provided in a central area of theelectrode, and said electrode further having, on a circumferential wallsurface surrounding said recess of said central area, a through portionpassing through bet surrounding said recess of said central area in saidwall surface.
 2. The electrode structure of the carrier substrate of thesemiconductor device according to claim 1, wherein said electrode ishemispheric configuration having a flange portion and having aconcentric hemispheric hollow portion thereinside, wherein saidhemispheric portion of said electrode being fitted into a hemisphericrecess provided on an outer surface of said carrier substrate of saidsemiconductor device, and said electrode being fixedly attached to saidcarrier substrate so that said flange portion abuts said outer surfaceof said carrier substrate.
 3. The electrode structure of the carriersubstrate of the semiconductor device according to claim 2, wherein saidthrough portion passing through between said recess and said outerportion of said wall surface being at least one slit portion provided insaid flange portion and said wall surface of said electrode adjacent tosaid flange portion.
 4. The electrode structure of said carriersubstrate of said semiconductor device according to claim 1, whereinsaid electrode is cylindrical having a flange portion and having aconcentric cylindrical hollow portion said reinside, said cylindricalportion of said electrode being fitted into a cylindrical recessprovided on an outer surface of said carrier substrate of saidsemiconductor device, and said electrode is fixedly attached to saidcarrier substrate so that said flange portion abuts said outer surfaceof said carrier substrate.
 5. Said electrode structure of said carriersubstrate of said semiconductor device according to claim 4, whereinsaid through portion passing through between said recess and said outerportion of said wall surface being at least one slit provided in saidflange portion and said cylindrical wall surface of said electrodeadjacent to said flange portion to a position close to a bottom.
 6. Theelectrode structure of the carrier substrate of the semiconductor deviceaccording to claim 1, wherein a package of said semiconductor device isof a BGA (ball grid array) type.
 7. The electrode structure of thecarrier substrate of the semiconductor device according to claim 1,wherein a package of said semiconductor device is of a CSP (chip scalepackage) type.